The overall objective of this proposal is to study gastrointestinal function by means of measurements of the absorption and excretion of intestinalgases or by techniques developed from our previous studies of bowel gases. The specific objectives and the techniques to be employed are as follows: quantitation of counter-current exchange in the gut by measuring the absorption of inert gases and carbon monoxide; quantitation of the diffusing capacity of the gut by carbon monoxide absorption measurements; study of villus and crypt blood flow using 7-10 microns microspheres; assess the frequency and magnitude of cabohydrate malabsorption using breath H2 measurements and assess the role of the colon in carbohydrate malabsorption; in clinical "gas" syndromes determine the source, rate of delivery and transit of duodenal gases using a perfusion technique and the source of colonic gas by measurement of H2 production and catabolism; and assess the in situ metabolism of the colonic flora by measurement of these volatile products in breath and blood.